Gate valves are generally used for opening and closing an opening leading to a vacuum chamber in a semiconductor manufacturing apparatus or the like, have a valve shaft to which a valve plate is attached, and an air cylinder connected to the valve shaft, and are configured to operate the valve shaft with the air cylinder, to thereby bring a seal member of the valve plate into and out of contact with a valve seat surface provided around the opening, and to thereby open and close the opening.
In relation to opening and closing the opening in gate valves, there are mainly known a method in which a valve shaft is rotated about a point, and the valve plate is thereby opened and closed, and a method in which a valve assembly composed of a valve shaft and a valve plate is moved perpendicularly to a valve seat surface, and the valve plate is thereby opened and closed.
A gate valve employing the latter method is capable of bringing the whole circumference of a seal member of a valve plate into and out of contact with a valve seat surface of the opening at the same time and thereby opening and closing the opening without sliding them relative to each other, is therefore called a non-sliding gate valve, is capable of suppressing twisting of the seal member, generation of abrasion powder, and so forth due to friction between the seal member and the seal surface, and therefore has attracted attention in recent years.
An example of such a non-sliding gate valve is disclosed in Patent Literature 1. The gate valve described in Patent Literature 1 has, as shown in FIG. 11 and FIG. 12, two cam grooves 130 formed in each of a pair of cam frames 128 fixed to drive rods 109 with a rod arm 124 therebetween in an oblique direction with respect to a valve seat surface 110, and two cam rollers 133 attached to each of the left side surface and the right side surface of a lever member 112 and fitted in the corresponding cam grooves 130. Stopping rollers 136 attached to the cam rollers 133 come into contact with contact portions 137 formed in roller frames 132. The cam frames 128 move upward with the upward movement of the lever member 112 stopped and a compression spring 125 compressed, and each cam groove 130 moves upward relative to the corresponding cam roller 133. Therefore, the cam rollers 133 are pressed by the groove walls of the sloping cam grooves 130, and the valve plate 105 and the valve shaft 107 move perpendicularly to the valve seat surface 110.